Andre Villas-Boas admits letting Steven Caulker leave Tottenham was one of the hardest decisions of his time at White Hart Lane.

Having come through the ranks, Caulker (above) was tipped to become Tottenham's long-term replacement for Ledley King.

The 21-year-old made 28 appearances for Villas-Boas last season and even earned an England cap, but the Tottenham manager surprisingly sold the centre-back to Cardiff for £8.5million this summer.

Villas-Boas stands by his decision, but he admits it was not one that he took lightly.

"Yes, it was one of the tougher decisions I have made here," the Tottenham manager said.

"At that time we were short at the back. We had just lost Jan (Vertongen) during the Hong Kong trip but we felt the price was right and it was an opportunity that we had to take."

It was not just the big money that was on the table from Cardiff that persuaded Villas-Boas to sell Caulker.

After winning his first cap against Sweden, the defender was keen to make sure that he was in Roy Hodgson's thoughts for next year's World Cup.

To do that, he would have to be playing on a regular basis, and despite the departure of William Gallas this summer, that was not something that Villas-Boas could offer.

"I can understand why people were surprised (that we sold him) because he was home-grown and he was a player who did well for us, but in the end we have great competition for places and we decided for Steven to move to another club," the Spurs manager said.

"He has high expectations towards his career, towards a first-team place and we decided to allow that transfer to happen."

Villas-Boas will see Caulker for the first time since he sold him when Tottenham travel to Cardiff for a potentially tricky away game later today.